<html><body>The convention is that method includes parentheses if it has <a href="http://en.wikipedia.org/wiki/Side_effect_(computer_science)">side effects</a>.

While it's possible to leave out empty parentheses in method calls (to adapt
the <a href="http://en.wikipedia.org/wiki/Uniform_access_principle">uniform access principle</a> to Java), it's recommended to still write the empty
parentheses when the invoked method represents more than a property of
its receiver object.

<small>* Refer to Programming in Scala, 10.3 Defining parameterless methods</small>
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